1. Field of the Invention
The present invention relates in general to cylinder head covers of an internal combustion engine and more particularly to the cylinder head covers of a type that is constructed of resin. More specifically, the present invention is concerned with a cylinder head cover of resin which exhibits a satisfied mechanical strength irrespective of a thinner wall and light-weight construction thereof.
2. Description of the Related Art
In order to clarify the present invention, one conventional cylinder head cover of the above-mentioned type, namely, the resin-made molded cylinder head cover disclosed in Japanese Laid-open Patent Application (tokkai) 2007-154812 will be briefly described.
The cylinder head cover disclosed by the above-mentioned publication comprises a thinner cover part that is rectangular in shape and a flange part that is integrally formed around a lower peripheral portion of the thinner cover part and has a thickness larger than that of the thinner cover part. The flange part is integrally formed at mutually spaced positions with a plurality of bolt boss portions each being cylindrical in shape. When in use, the flange part of the cylinder head cover is put on a cylinder head of an internal combustion engine having a rectangular (or rectangularly extending) gasket intimately put therebetween and a plurality of connecting bolts passing through the bolt boss portions are used to tightly fix the cylinder head cover to the cylinder head. Usually, cylinder head covers of the above-mentioned type are constructed of glass fiber-reinforced polyamide resin or the like.
As is mentioned hereinabove, the flange part of the cylinder head cover of the above-mentioned publication is formed thicker than the cover part. This is because of need of increasing the mechanical strength of the flange part to which a remarkably large force is applied from the connecting bolts at the time when the bolts are turned for fixing the cylinder head cover to the cylinder head of the engine. If the cylinder head covers are of a type that has a gasket receiving groove at a lower surface of the thicker flange part, the thickness of the flange part needs to increase more by a degree corresponding to a mechanical strength that would be lost due to presence of the gasket receiving groove.
Due to the above-mentioned reasons, it has been difficult to sufficiently reduce the thickness of the flange part of the cylinder head cover and weight of an entire construction of the cylinder head cover.